During the last decade the nanomaterials
have emerged as the new building blocks to construct light energy harvesting
assemblies. Organic and inorganic hybrid structures that exhibit improved
selectivity and efficiency towards catalytic processes have been designed. Size dependent properties such as size
quantization effects in semiconductor nanoparticles and quantized charging
effects in metal nanoparticles provides the basis for developing new and
effective systems. These nanostructures provide innovative
strategies for designing next generation energy conversion devices. Recent efforts to synthesize
nanostructures with well defined geometrical shapes (e.g., solid and hollow
spheres, prisms, rods, wires) and their assembly as 2- and 3- dimensional
assemblies has further expanded the possibility of developing new strategies
for light energy conversion.

There are three major ways that one can utilize
nanostructures for the design of solar energy conversion devices. The
first one is to mimic the photosynthesis with donor-acceptor molecular assemblies
and clusters. The second one is the
semiconductor assisted photocatalysis to produce fuels such as hydrogen. The
third and most promising category is the nanostructure semiconductor based
solar cells. Strategies to employ ordered assemblies of
semiconductor and metal nanoparticles, inorganic-organic hybrid assemblies and
carbon nanostructures in the energy conversion schemes are currently being explored in our laboratory.

To elucidate the
interfacial charge transfer processes in semiconductor/sensitizer
systems.

To improve
photoinduced charge separation in donor-acceptor type dyads and triads
by
binding them to metal nanostructures and/or semiconductor composites

To employ
donor-acceptor based supramolecular systems (for example, fullerenes
and porphyrins) and molecular clusters for in
organic photovoltaic cells.

Thanks
to
our collaborators
Profs. S. Hotchandani
(Univ. Of Tros Riveres, Canada) Prof. K. George Thomas (RRL,
India) and Prof. S. Fukuzumi (Osaka Univ., Japan) who
have collaborated on the projects related to our solar energy
conversion research . We also acknowledge thr continued
research funding by the Department of Energy, Office of Basic Energy
Sciences

Recent
Progress

Pioneered in the elucidation of interfacial charge transfer
processes and introduction of composite semiconductor systems for
improving the performance of dye sensitized solar cells

Probed
the role of iodide and triiodide ions in deactivating the excited state
of Ru(II)polypyridyl complex bound to TiO2.

Established
the role of Fermi level equilibration in improving the energetics of
semiconductor-metal systems. A shift of 100-150 mV in the
apparent Fermi level was achieved by depositing 2-3 nm Au nanoparticles
on TiO2 nanostructures.

Achived
a photoconversion efficiency (IPCE ) of
60% and power
conversion effeciency of 2% using Au-Porphyrin_C60 based molecular
clusters.

Designed
inorganic-organic hybrid assemblies for photoelectrochemical conversion
of light energy